How [18F]FDG-PET/CT Affects the Management of Patients with Differentiated Thyroid Carcinoma in Clinical Routines

Purpose: To investigate the impact of [F-18]FDG-PET/CT on the management of differentiated thyroid carcinoma (DTC) in routine clinical settings. Material and methods: In total, 98 patients (55 females, age 56 +/- 18 years) with histologically confirmed thyroid cancer, including all types of DTC and poorly differentiated thyroid cancer (PDTC, n = 7), underwent [F-18]FDG-PET/CT for staging or recurrence diagnostics performed using a state-of-the art clinical scanner (Biograph mCT, Siemens Healthineers) with a standardized examination protocol. The impact of PET/CT on clinical decision making was prospectively evaluated using standardized questionnaires completed by the referring physicians before and after PET/CT. Patient outcome was analyzed for OS drawn from patient records. Results: Referring physicians were unable to establish a treatment plan for 81% of patients with thyroid cancer in the absence of PET/CT. The use of PET/CT had a notable influence on patient management, leading to the development of a well-defined treatment plan for 92% of patients. Moreover, after PET/CT a change in pre-PET/CT-intended treatments occurred in 32% of cases, and further invasive diagnostic could be waived in 7% of cases. [F-18]FDG-PET/CT revealed a tumor detection rate of 68% (local tumor: 19%, lymph node metastases: 40%, distant metastases: 42%). HTg levels, when stimulated via TSH, were considerably higher in patients with metastases detected on PET/CT, compared to those without metastatic findings (p = 0.02). OS was significantly worse in patients with PDTC (p = 0.002) compared to follicular thyroid cancer (FTC) and PTC or even in patients with distant metastases at first diagnosis (p = 0.03). Conclusions: This prospective registry study confirms that [F-18]FDG-PET/CT used in a routine clinical setting has a very important impact on the management of patients with thyroid cancer by initiating treatments and reducing the uses of additional imaging and invasive tests.